lora/lorawan: implement minimal Join() function, and supporting functions

Signed-off-by: deadprogram <ron@hybridgroup.com>

lora/lorawan/adaptor.go

@@ -1,8 +1,16 @@
 package lorawan
 
-import "tinygo.org/x/drivers/lora"
+import (
+	"errors"
 
-var ActiveRadio lora.Radio
+	"tinygo.org/x/drivers/lora"
+)
+
+const LORA_RXTX_TIMEOUT = 1000
+
+var (
+	ActiveRadio lora.Radio
+)
 
 func UseRadio(r lora.Radio) {
 	if ActiveRadio != nil {
@@ -11,7 +19,55 @@ func UseRadio(r lora.Radio) {
 	ActiveRadio = r
 }
 
-func Join() error {
+func Join(otaa *Otaa, session *Session) error {
+	var resp []uint8
+
+	if ActiveRadio == nil {
+		return errors.New("no LoRa radio attached")
+	}
+
+	otaa.Init()
+
+	// Send join packet
+	payload, err := otaa.GenerateJoinRequest()
+	if err != nil {
+		return err
+	}
+
+	ActiveRadio.SetCrc(true)
+	ActiveRadio.SetIqMode(0) // IQ Standard
+	ActiveRadio.Tx(payload, LORA_RXTX_TIMEOUT)
+	if err != nil {
+		return err
+	}
+
+	// Wait for JoinAccept
+	//println("lorawan: Wait for JOINACCEPT for 10s")
+	ActiveRadio.SetIqMode(1) // IQ Inverted
+	for i := 0; i < 15; i++ {
+		resp, err = ActiveRadio.Rx(LORA_RXTX_TIMEOUT)
+		if err != nil {
+			return err
+		}
+		if resp != nil {
+			break
+		}
+	}
+	if resp == nil {
+		return errors.New("no JoinAccept packet received")
+	}
+	//println("lorawan: Received packet: len=", len(resp), "payload=", bytesToHexString(resp))
+
+	err = otaa.DecodeJoinAccept(resp, session)
+	if err != nil {
+		return err
+	}
+	// println("lorawan: Valid JOINACCEPT, now connected")
+	// println("lorawan: |  DevAddr: ", bytesToHexString(r.Session.DevAddr[:]), " (LSB)")
+	// println("lorawan: |  NetID  : ", bytesToHexString(r.Otaa.NetID[:]))
+	// println("lorawan: |  NwkSKey: ", bytesToHexString(r.Session.NwkSKey[:]))
+	// println("lorawan: |  AppSKey: ", bytesToHexString(r.Session.AppSKey[:]))
+
 	return nil
 }